1. Field of the Invention
This invention relates to paste-form detergents and to a process for their production.
2. Discussion of Related Art
Detergents used in the home are adapted to meet the requirements arising in that environment. Thus, normally they are powders or are sufficiently liquid to be able to be poured out and dosed without difficulty. Since liquid detergents are also expected to be stable in storage over relatively broad temperature ranges, organic solvents and/or hydrotropes are often added to them although they do not make any contribution to the washing or cleaning result and are undesirable for that reason. One way of overcoming possible dosing problems with detergents that are not sufficiently liquid is proposed in European patent application EP 253 151 A2. This document relates to liquid and, in some cases, highly viscous detergents based on nonionic and anionic surfactants which contain polyethylene glycol as hydrotrope and which do not have to be dosed by the user in liquid form, but instead are packed in portions in bags of a water-soluble material, for example polyvinyl alcohol.
The paste-form detergent described in European patent EP 295 525 B1 consists of a phase formed from nonionic surfactant which is liquid at temperatures below 10.degree. C. and a solid phase with a certain particle size dispersed therein which is formed from washing alkalis, sequestering agents and optionally anionic surfactants. The surfactants or surfactant mixtures used must have a pour point (solidification point) below 5.degree. C. to avoid solidification of the paste at low transportation and storage temperatures. This detergent paste is intended for institutional laundries and is so free-flowing that it can be pumped by a standard feed pump through a suction line. However, it has been found that pastes of the type in question are not always able satisfactorily to guarantee the homogeneity of their ingredients during the production process and, in many cases, also tend to separate in storage. This applies not only to the separation of the solid constituents from the liquid constituents, but also to the phase separation of the liquid ingredients.
International patent application WO 95/09229 describes another paste-form detergent which contains as its nonionic surfactant 40 to 70% by weight of ethoxylated C.sub.10-20 fatty alcohol liquid at room temperature with an average degree of ethoxylation of 1 to 8 and 20 to 50% by weight of ethoxylated and propoxylated C.sub.10-20 fatty alcohol liquid at room temperature with an average degree of ethoxylation of 2 to 8 and an average degree of propoxylation of 1 to 6 and 1 to 10% by weight of soap. This paste-form detergent is so pseudo-plastic that it does not flow under the effect of gravity at room temperature, but develops a distinctly lower viscosity on exposure to shear forces and then flows under the effect of gravity. This paste-form detergent is preferably dosed by subjecting it to shear forces to reduce its viscosity and dosing the now flowable detergent by feed pumps.
Recently, the demand to dispense with detergent ingredients which have been found to show inadequate biodegradability has also arisen in institutional laundries. This demand is particularly difficult to meet because the performance of the detergents has to satisfy far more stringent requirements by comparison with the conditions prevailing in domestic washing. This applies in particular to the surface-active ingredients which make a particularly crucial contribution towards the cleaning result and among which synthetic anionic surfactants, particularly of the sulfonated alkyl benzene type, play a leading role in this regard.
Accordingly, the problem addressed by the present invention was to provide a paste-form detergent for use in institutional laundries which would combine high stability in storage with high washing performance in the absence of synthetic anionic surfactants of the alkyl benzenesulfonate type normally required to that end.
This problem has largely been solved by optimizing the nonionic surfactant component and by using long-chain alcohols and/or long-chain alkyl ethers.